Cut citrus fruit in half and squeeze juice into a jug. With each squeezed segment run knife along edge to capture any juicy bits. Don’t worry about pips falling in – pips and pith contain pectin and help turn the final product into jam.

Cut skins (1 orange skin and 1/4 grapefruit) into thin slithers, not worrying too much about attached piths – they’ll dissolve in the cooking process and help the jam set.

Soak skin slithers in 1 pint water overnight.

The next day, bring all ingredients (including water in which skins have soaked + remaining water) to boiling point in a large pan over high flame. Boil rapidly for 20 minutes, then reduce flame – continue to simmer or 20 minutes. Test to see whether the jam is ready – drop a small amount onto a chilled dish – the splodge should wrinkle when pushed.

Pick out any pips and pour jam into sterilised jars, seal and wait until cool before placing jars into fridge.